Goals for the forthcoming year are: a) to characterize certain temperature sensitive mutants of S. cerevisiae by genetic and biochemical methods. The mutants will be mapped and ribosomes will be examined for possible protein modification. b) to prepare hybrid yeasts from parents of various species and to analyze the segregation patterns of ribosomal proteins in these hybrids. c) to analyze the properties of ribosomes of those yeasts that are "naturally" resistant to antibiotics such as blasticidin, cycloheximide, trichodermin, etc. Are these resistances ribosomal? d) to characterize the cloned yeast DNA fragments that encode genes (ribosomal proteins?) that complement known antibiotic resistance alleles and to continue recombinant DNA experiments (using different enzymes) to obtain additional gene sequences. e) to study the nature of the plasmids formed by transformation of yeasts with bacterial phosphotransferase genes and to develop these as cloning vectors.